Pyrolytic decomposition of silicon-bearing gas in fluidized beds is an attractive process for producing polysilicon for the photovoltaic and semiconductor industries due to excellent mass and heat transfer, increased surface for deposition, and continuous production. Compared with a Siemens-type reactor, the fluidized bed reactor offers considerably higher production rates at a fraction of the energy consumption. The fluidized bed reactor can be continuous and highly automated to significantly decrease labor costs.
A common problem in fluidized bed reactors is fouling of the nozzle and surrounding reactor walls as silicon deposits form around the nozzle opening and on the walls. Silicon-bearing gas also may decompose and deposit silicon within the nozzle if the temperature is sufficiently high. Another common problem is contamination of the fluid bed at high operating temperatures by materials used to construct the reactor. For example, nickel has been shown to diffuse into a silicon layer from the base metal in high-nickel alloys.